A desirable feature of copying machines is the capability of allowing the machine operator to select the size copy paper on which the projected image in the machine will be copied. Such copying machines may be used to reproduce the visual image on the original document at its actual size as with the case of the typical office copier, at an enlarged size as with the case of micrographic reader-printers for microfilm and/or microfiche, or at a reduced size as with the case of reducing copying machines. Some copying machines have attempted to solve this problem by allowing the operator to insert different size sheets of copy paper into the machine. Still other machines have conveniently fed the copy paper through the machine from a continuous supply roll with the copy paper being cut by a paper cutter in the machine to a length selected by the machine operator.
These machines usually located the copy paper in exposure position using the leading edge of the cut sheet of copy paper by always stopping the leading edge of the copy paper at the same position, that position being one edge and corner of the largest possible exposure area in the machine. This usually requires that the original document medium being reproduced be placed along one edge or one corner of the document carrying area of the machine if the document carrying area is fixed in the machine or, if the document carrying area can be shifted in the machine, usually requires that the original document medium be positioned so that the projected image from the original document medium be aligned with one edge or one corner of the projected image area in the machine. This is because the edge or corner of the projected image in the machine must always lie in registration with the leading edge of the copy paper stopped at the edge or corner of the largest exposure area in the machine. This has not been particularly successful in micrographic reader-printers inasmuch as it is relatively difficult to locate the micrographic film in the proper position on the image projection area to always assure that the film image is located properly for copying on the copy paper. Another problem in using this registration technique with micrographic reader-printers is that the resolution of the optical system which projects the film image onto the copy paper is usually best along the center of the image projection area of the reader-printer and, having to locate the film image away from this central position, many times results in a significant loss of resolution in the copied document. Thus, it will be seen that the prior art has been relatively unsuccessful, especially with micrographic reader-printers in solving the problem of cutting the copy paper to any desired length while still allowing the film image to be conveniently located centrally in the image projection area for best resolution.
Yet another problem associated with these prior art copying machines is that no visual correlation between the size of the copy paper selected for copying and that portion of the image to be copied is usually provided. Even if some visual correlation is provided, it is relatively difficult to use and generally requires guesswork on the part of the operator to properly locate the original document. This is especially true where an infinite number of copy paper lengths can be selected over the range of the machine.